上海交通大学：《Design & Manufacturing II and Project》课程教学资源（讲义）Lecture 3 Electric Motors

ME357 Mechanical Design and Manufacturing ll Electric Motors Principles and Applications 1

1 ME 357 Mechanical Design and Manufacturing II Electric Motors Principles and Applications

Lectures ME350 Power/Energy Conversion (Electrical Motors) Power/Energy Transmission (Gears, Belt Drives, Power Screws) Joints Transmission (Fasteners, Support Structural Connectors) (Bearings) Support (Frames Shafts Axles Spindles) Tools Stress Analysis, Failure Theories Dynamics,Statics,Etc.... 2

2 ME 350 Lectures Power/Energy Conversion (Electrical Motors) Power/Energy Power/Energy Conversion Conversion (Electrical Motors) (Electrical Motors) Power/Energy Transmission (Gears, Belt Drives, Power Screws) Transmission Support (Bearings) Joints (Fasteners, Connectors) Structural Support (Frames Shafts Axles Spindles) Tools Stress Analysis, Failure Theories Dynamics, Statics, Etc…

Power/Energy Converters ME350 Rotary >Electrical Input->Mechanical Rotary Motion/Torque =DC Motor(直流电机) =AC Motor(交流电机) =Stepper Motor(步进电机) >Combustion -Mechanical Rotary Motion /Torque =Gasoline Engine(发动机) =Gas Turbine（燃气轮机) 3

3 Power/Energy Converters ME 350 • Rotary ¾Electrical Input -> Mechanical Rotary Motion/Torque =DC Motor DC Motor（直流电机） =AC Motor（交流电机） =Stepper Motor（步进电机） ¾Combustion -> Mechanical Rotary Motion /Torque =Gasoline Engine（发动机） =Gas Turbine（燃气轮机）

Power/Energy Converters ME350 ●Linear >Electrical Input->Mechanical Linear Motion/Torque or force Solenoids =Leadscrew linear actuators(丝杠线性执行机构) =Solenoids（电磁铁或螺线管) >Pressure -Mechanical Linear Motion/Torque or force =Hydraulic Pumps(液压泵) =Hydraulic Actuators(液压动力装置) =Pneumatic Actuators(气动动力装置) =Compressors(压缩机) 4

4 Power/Energy Converters ME 350 • Linear ¾Electrical Input -> Mechanical Linear Motion/Torque or force =Leadscrew linear actuators（丝杠线性执行机构） =Solenoids（电磁铁或螺线管） ¾Pressure -> Mechanical Linear Motion/Torque or force =Hydraulic Pumps（液压泵） =Hydraulic Actuators（液压动力装置） =Pneumatic Actuators（气动动力装置） =Compressors（压缩机） Solenoids

Electric Motors ME350 Electric Motors convert electrical power to mechanical power. Electrical Power Mechanical Power Electric Motor 1,V F,vorT,o /Current F:Force T:Torque V:Voltage v:Velocity o:Angular Velocity Electrical Power=I*V Mechanical Power F*v for linear motor T*o for rotary motor Electric motors normally i mean electromagnetic motors. They use the principles of electromagnetism for electrical/mechanical power conversion.s

5 ME 350 Electric Motors • Electric Motors convert electrical power to mechanical power. Electric Motor Electrical Power I, V Mechanical Power F, v or T, ω I : Current V: Voltage F: Force v: Velocity T: Torque ω: Angular Velocity • Electric motors normally mean electromagnetic motors. They use the principles of electromagnetism for electrical/mechanical power conversion. Electrical Power = I*V Mechanical Power = F*v for linear motor = T* ω for rotary motor

Electric Motors ME350 Basic types >DC Motors:speed and rotational direction control via voltage 二 Easy to control torque via current low voltage 二 linear torque-speed relations 三 Quick response >AC Motors:smaller,reliable,and cheaper 二 speed fixed by AC frequency 二 low torque at low speed 二 difficult to start 6

6 ME 350 • Basic types ¾DC Motors: speed and rotational direction control via voltage = Easy to control torque via current = low voltage = linear torque-speed relations = Quick response ¾AC Motors: smaller, reliable, and cheaper = speed fixed by AC frequency = low torque at low speed = difficult to start Electric Motors

Objectives of this Lecture ME350 Describe the factors that must be specified to select a suitable motor Describe the principles of operation of DC motors. Describe the general form of a motor performance curve. Describe the advantages and disadvantages of DC motors compared with AC motors. Describe four basic designs of DC motors,and describe their performance curves. 7

7 ME 350 Objectives of this Lecture • Describe the factors that must be specified to select a suitable motor • Describe the principles of operation of DC motors. • Describe the general form of a motor performance curve. • Describe the advantages and disadvantages of DC motors compared with AC motors. • Describe four basic designs of DC motors, and describe their performance curves

DC Motors:Principles of Operation ME350 A wire carrying current experiences a force in a magnetic field. F-(lx B) Magnetic Flux Density(磁通量) Induced force (Tesla) Current Length of wire in the (amp) direction of i(m) IxB I×B=|IBsin B 8

8 ME 350 DC Motors: Principles of Operation • A wire carrying current experiences a force in a magnetic field. Magnetic Flux Density (磁通量) (Tesla) = i l ×BF )( Induced force Current (amp) Length of wire in the direction of i (m) ×BI I B θ =× BIBI sin θ

Electromagnetic Force ME350 A wire carrying current in a magnetic field. D F=ilB (1 wire length) Note:a dot will represent a current out of the page and a cross(x)will represent a current into the page. 9

9 ME 350 Electromagnetic Force • A wire carrying current in a magnetic field. B i F = ilB ( l = wire length) Note: a dot will represent a current out of the page and a cross( ×) will represent a current into the page

Electromagnetic Force ME350 The force is perpendicular to both the magnetic field and current F B 10

10 ME 350 Electromagnetic Force • The force is perpendicular to both the magnetic field and current